1. Field of the Invention
This invention relates generally to flexible shaft couplings and more particularly to couplings utilizing a yielding disc element for transmitting rotary motion between substantially coaxially aligned shafts.
2. Description of the Prior Art
Shaft couplings using flexible metal diaphragms to compensate for misalignment of the connected shafts are well known. Such couplings use yielding metal diaphragms or discs, connected to hubs on the shafts, that flex during rotation to accommodate shaft misalignment. Examples of such couplings are shown in Troeger et al. U.S. Pat. No. 2,883,839, Anderson et al. U.S. Pat. No. 3,808,837 and Jencick U.S. Pat. No. 1,283,787.
Shaft couplings using flexible metal diaphragms are subject to two inherent disadvantages which heretofore consistently troubled prior art couplings. The first problem is that flexible metal diaphragm couplings are capable of axial vibrations. The critical frequency of the vibrations often falls within the operating speed range of the coupling, an occurrence which often leads to coupling failures. The prior art has sought to minimize this problem by either increasing the weight of the floating shaft to decrease the critical frequency; or to use a stiffer disc thereby increasing the critical frequency. Both prior art solutions have not proved satisfactory. The former causes the coupling to go through its critical frequency while the machinery is coming up to operating speed and the latter limits the maximum axial movement of the floating shaft between the fixed shafts, which movement is originally very limited. The second disadvantage of flexible metal disc couplings is that they are very sensitive to corrosion. While presently the discs are covered with various protective coatings, the coatings have not been successful in resisting the many environments, oil, sand, hydrogen, chlorides, etc. in which which couplings are used.
Accordingly, it is the general object of this invention to provide a shaft coupling using flexible metal diaphragms which are not susceptible to failures from axial vibration or corrosion.